Rapid Preoperative Preparation for Severe Hyperthyroid Graves’ Disease

Abstract

Panzer et al. (1) presented an interesting approach for the rapid preoperative preparation of hyperthyroid Graves’ disease patients, using multiple-level blocking of the thyroid hormones’ synthesis-secretion-activation cascade, suggesting that an average 7-d treatment is sufficient to restore euthyroidism in severely thyrotoxic patients. The data presented indicate preoperative normalization of total T3, whereas total T4 and free T4 index remain somewhat increased. Although the study clearly demonstrates the clinical feasibility and safety of the protocol, I would like to point to a possible pitfall in the definition of euthyroidism in those patients. We (2) have shown that after withdrawal of T4 replacement in athyreotic patients, the half-life time (t1/2) of the free thyroid hormones is considerably longer than the t1/2 of the total T4 and total T3 (7 and 0.8 d, respectively). We observed a mean free T4 t1/2 of 11 d (range, 8–13 d) and mean free T3 t1/2 of 15.5 d (range, 12–19 d). The longer t1/2 of the free hormones was attributed to release of T4 from binding proteins and continuous production of T3 from T4 in the periphery. Thus, attainment of euthyroidism according to total thyroid hormone measurements may not correspond in time with biochemical euthyroidism according to free hormone measurements. Because the study of Panzer et al. (1) included blocking of T4 to T3 conversion, which was not part of our study, the free T3 t1/2 in that circumstance may still be different from that observed in our study. It would be interesting to follow up on their study with current free T4 and free T3 assays. An unfortunate practical problem that may impede the current ability to use this protocol is, of course, the withdrawal from the market of oral iodinated radiographic contrast agents.